The present invention relates to a variable displacement type compressor and, more particularly, such a compressor comprising a casing having a working chamber internally defined therein and a plurality of cylinder bores provided therein opened to face to the working chamber. A driving shaft is rotatably carried in the casing with the cylinder bores axially aligned with and disposed around the driving shaft. A working piston is slidably received in each of the cylinder bores. A sleeve is axially slidably fitted over the driving shaft within the working chamber. A holder is carried on the sleeve for swinging movement about an axis perpendicular to an axis of the driving shaft and is connected to the driving shaft. A swingable swash plate is carried on the holder and is connected to the working pistons through connecting rods. A control piston is connected to the sleeve and slidably received in the casing so as to vary the angle of inclination of the holder and the swingable swash plate to vary the operation stroke of the working pistons. Stroke detecting means is provided for detecting the operation stroke of the working pistons.
A variable displacement type compressor is known, for example, from Japanese Patent Application Laid-open No. 218670/87 or the like, in which the operation stroke of the working pistons is varied by controlling the angle of inclination of a swash plate swingable about an axis perpendicular to an axis of a driving shaft, and with the variation of the operation stroke, the discharge amount is varied.
In such compressor, however, it is necessary to detect the operation stroke of the working pistons for the purpose of controlling the operation stroke of the working pistons and detecting any trouble. In the above compressor, a position detector is provided in the casing, which generates an electric pulse signal whenever an object to be detected, provided on the swingable swash plate passes through sensing range of the position detector. In such a position detector for detecting the operation stroke by detection of the swinging motion of the swingable swash plate, however, the detection of the stroke is possible only when the swingable swash plate is swung. The operation stroke cannot be detected before starting of the operation of the compressor. For this reason, when the operation of the compressor is started in a region of slow speed (lower revolutions) of an engine connected to the driving shaft (e.g., during idling), it is not obvious that the number of revolutions of the engine should be set at what level and in addition, it is impossible to set the amount of fuel supplied to the engine sufficient to maintain the number of revolutions.
The present invention has been accomplished with such circumstances in view, and it is an object of the present invention to provide a variable displacement type compressor wherein the stroke of the working pistons can be detected even before starting of the operation of the compressor.